Noah Cover created NIFI-16174:
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Summary: Controller-service reference start/stop does not treat a
stateless process group as a single lifecycle unit
Key: NIFI-16174
URL: https://issues.apache.org/jira/browse/NIFI-16174
Project: Apache NiFi
Issue Type: Bug
Reporter: Noah Cover
When schedulable components that reference a controller service are started or
stopped
via the controller-service "references" path, processors that live inside a
stateless
process group are scheduled *individually* instead of through their owning
stateless
group. A stateless group is a single scheduling unit
(ExecutionEngine.STATELESS), so
individual scheduling leaves the group in an inconsistent state: some member
processors
stopped, others running, while the stateless group node itself stays RUNNING.
The group
cannot then recover cleanly.
* org.apache.nifi.controller.service.StandardControllerServiceProvider
** unscheduleReferencingComponents(...) stops each referenced processor
directly via
ProcessGroup.stopProcessor(node), regardless of stateless membership.
** scheduleReferencingComponents(...) starts each referenced processor via
ComponentScheduler.startComponent(node). For a stateless member,
DefaultComponentScheduler.startNow(...) skips the processor, so the start is
a silent
no-op and the group is never actually started as a unit.
* Reached through PUT /controller-services/\{id}/references
(state=RUNNING|STOPPED) ->
StandardControllerServiceDAO.updateControllerServiceReferencingComponents(...).
* verifyUpdateReferencingComponents(...) only checks the *service's own*
process group,
so a service defined at a STANDARD (root) scope does not block the request
even when the
referencing processors live inside a stateless child group.
Real connectors hit this during break-glass / troubleshooting operations.
Example: the
Snowflake CDC connectors define a Snowflake connection-pool controller service
at the
connector root that is referenced by processors inside a stateless subgroup
(e.g. the
"Create Journal Table" group). Stopping the service's referencing components
leaves that
stateless group with a mixed processor state and a stuck group node, and the
connector
does not return to a clean RUNNING state without a full stop/restart.
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